Perkins NJ Series Troubleshooting Manual page 7

SENR9982-01
The engine is designed for electronic control. The
engine has an Electronic Control Module (ECM),
a fuel rail pump and electronic unit injectors. All of
these items are electronically controlled. There are
also a number of engine sensors. Turbocharged
engines can be equipped with an electronically
controlled wastegate for the turbocharger. The ECM
controls the engine operating parameters through
the software within the ECM and the inputs from the
various sensors. The software contains parameters
that control the engine operation. The parameters
include all of the operating maps and customer
selected parameters.
The electronic system consists of the ECM, the
engine sensors and inputs from the parent machine.
The ECM is the computer. The flash file is the
software for the computer. The flash file defines the
following characteristics of the engine:
• Engine power
•
Torque curves
•
Engine speed (rpm)
• Engine Noise
• Smoke and Emissions
The ECM determines the injection timing, the amount
of fuel that is delivered to the cylinders and the intake
manifold pressure if an electronically controlled
wastegate is installed on the turbocharger. These
decisions are based on the actual conditions and the
desired conditions at any given time.
Engine Speed Governor
The governor has software that compares the desired
engine speed to the actual engine speed. The actual
engine speed is determined through the primary
speed/timing sensor and the secondary speed/timing
sensor. If the desired engine speed is greater than
the actual engine speed, the governor injects more
fuel in order to increase engine speed. If the actual
engine speed is greater than the desired engine
speed, the governor limits the amount of fuel that is
supplied to the electronic unit injectors in order to
reduce engine speed.
Timing Considerations
Fuel injection timing is determined by the ECM after
considering input from the following components:
• Engine coolant temperature sensor
•
The sensor for the intake manifold air temperature
• The sensor for the intake manifold pressure
• Speed/timing sensors
• Throttle position sensor
At engine start-up, the ECM determines the top
center position of the number 1 cylinder from the
speed/timing sensors. The ECM determines when
fuel injection should occur relative to the top center
position. The ECM optimizes engine performance
by control of each of the electronic unit injectors so
that the required amount of fuel is injected at the
precise point of the engine's cycle. The electronic unit
injectors are supplied with high pressure fuel from
the fuel rail. The ECM also provides the signal to the
solenoid in the fuel rail pump. The solenoid in the fuel
rail pump controls a valve in the fuel rail pump. This
valve controls the pressure in the fuel rail. Fuel that is
not required for the engine is diverted away from the
fuel rail pump back to the fuel tank.
The ECM adjusts injection timing and fuel pressure
for the best engine performance, the best fuel
economy and the best control of exhaust emissions.
Fuel Injection
The flash file inside the ECM sets certain limits on
the amount of fuel that can be injected.
The Fuel Ratio Control Limit is a limit that is based
on intake manifold pressure and engine rpm. The
FRC Limit is used to control the air/fuel ratio in order
to control the engine's exhaust emissions. When
the ECM senses a higher intake manifold pressure,
the ECM increases the FRC Limit. A higher intake
manifold pressure indicates that there is more air in
the cylinder. When the ECM increases the FRC Limit,
the ECM allows more fuel into the cylinder.
The Rated Fuel Limit is a limit that is based on the
power rating of the engine and on the engine rpm.
The Rated Fuel Limit enables the engine power and
torque outputs to conform to the power and torque
curves of a specific engine model.
These limits are in the flash file and these limits
cannot be changed by the operator.
Diagnostic Codes
When the ECM detects an electronic system fault,
the ECM generates a diagnostic code. Also, the ECM
logs the diagnostic code in order to indicate the time
of the occurrence of the fault. The ECM also logs the
number of occurrences of the fault. Diagnostic codes
are provided in order to indicate that the ECM has
detected an electrical fault or an electronic fault with
the engine control system. In some cases, the engine
performance can be affected when the condition that
is causing the code exists.
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Troubleshooting Section